The invention relates generally to a WDM (Wavelength Division Multiplexing) optical communication system, more particularly, to a multi-channel light source generator in a WDM optical communication system using a single multiplexer/demultiplexer.
In order to increase the transmit capacity in the field of optical communications, study on a WDM scheme using a multi-channel light source has recently been actively made. At this time, the multi-channel light source in the WDM system employs a scheme by which an optical signal to be transmitted is applied to its assigned wavelength. A light source now widely used is a DFB-LD (Distributed Feedback Laser Diode). However, the laser diode is expensive and also requires its wavelength to be precisely controlled, since it must control the temperature to adjust its output wavelength.
FIG. 1 is a diagram of a conventional multi-channel light source generator. A plurality of multi-channel optical fiber lasers 12 which are serially connected, are connected to a pumping laser 11. A first WDM coupler 13 directs the pump light through the multi-channel optical fiber lasers 12 from the pumping laser 11, some of which are transmitted to an optical fiber 15 and some of which are inputted to an erbium-doped optical fiber 16 through an optical isolator 14 so that they can be amplified. Both the lights transmitted through the optical fiber 15 and the erbium-doped optical fiber 16 are combined at a second WDM coupler 17 and is then transmitted to optical isolator 18, which produces multi-channel output light 19.
At this time, as many as the multi-channel optical fiber lasers are connected, the internal loss of the optical fiber laser is increased. Also, as the light approaches the wavelength of the pump laser, the intensity of the multi-channel output light is reduced. However, this has a drawback that the quality of the transmittance is reduced since optical signal versus noise ratio is increased in a WDM optical transmit system using a WDM light source.
The present invention is contrived to solve the problems described above and the purpose of the disclosed embodiments of the present invention to provide a multi-channel light source generator in a WDM optical communication system, capable of outputting its pump light having the same intensity, reducing its intensity of noise and easily controlling the intensity of lights depending on respective wavelengths.
In order to accomplish the foregoing, a multi-channel light source generator in a WDM optical communication system according to a first aspect of the present invention is provided to include a pumping laser source for generating a pumping laser having a predetermined wavelength, a multi-channel light source generating means for generating multi-channel light sources using the pumping laser, a light separating means for separating the pumping laser and the multi-channel light sources, a demultiplexing means for separating the multi-channel light sources into a plurality of individual light sources, an intensity adjusting means for adjusting an intensity of the individual light sources, and a multiplexing mean for combining the individual light sources outputted from the intensity adjusting means.
Preferably, the demultiplexing means and the multiplexing means are comprised of a single multiplexing/demultiplexing means.
More preferably, the generator further comprises a reflecting means for redirecting the pumping laser separated by said light separating means to the multi-channel light source generating means.
Also, according to a second aspect of the present invention, a multi-channel light source generator in a WDM optical communication system is provided to include a multi-channel light source generating means for generating multi-channel light sources using a pumping laser and erbium-doped optical fiber Bragg gratings, a light separating means for separating the signal from the multi-channel optical fiber Bragg gratings into the multi-channel light source and a pumping light, a reflecting means for redirecting the pumping light separated by the light separating means to the optical fiber Bragg gratings, a demultiplexing means for separating the multi-channel light sources into individual light sources, a light attenuation means for individually attenuating the light signals separated by the individual light sources so that the intensity of the light can be made constant, and a multiplexing means for combining the individual light sources outputted from the light attenuation means.
Preferably, the de-multiplexing means and the multiplexing means are comprised of a single multiplexing/demultiplexing means.
More preferably, the reflecting means is a pumping light reflecting coating element.